Kinetics and Mechanism of Hydrolysis of Insecticidal $O,O-diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothiate\;(Volaton^{\circledR})$

살충성 $O,O-Diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothioate\;(Volaton^{\circledR})$의 가수분해 반응메카니즘

The rate of hydrolysis of insecticidal $O,O-diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothioate\;(Volaton^{\circledR})$ has been studied in 25% (v/v) aqueous dioxane. On the basis of solvent effect (pH 6.0; m=0.21, n=1.55, pH 12.0; m=0.42, n=3.14 & $|m|{\ll}|l|$), general base catalysis, hydrolysis product analysis, calculation of molecular orbital (MO) and rate equation, it may be concluded that the hydrolysis of Volaton proceeds through the $A_{AC}2$ mechanism via trigonal bipyramidal $(sp^3d^2)$ intermediate below pH 7.0, while above pH 9.0 the hydrolysis proceeds through the $B_{AC}2$ mechanism. Hydrolysis reactivity of Volaton depends on positive charge strength $(p{\gg}{\alpha}C_2)$ rather than steric hindrance. In the range between pH 7.0 and pH 9.0, these two reactions occur competitively.

25%(v/v) dioxane 수용액의 넓은 pH범위에서 살충성 $O,O-Diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothioate(Volaton^{\circledR})$의 가수분해 반응은 용매효과 (pH 6.0; m=0.21, n=1.55, pH 12.0; m=0.42, n=3.14 및 $|m|{\ll}|l|$), 반응 속도식, 일반염기 촉매효과, 가수분해 반응생성물 분석 및 분자 궤도(MO) 함수 계산 등의 결과로부터 trigonal bipyramidal$(sp^3d^2)$중간체를 경유하여 pH 7.0 이하에서는 $A_{AC}2$형 반응, 그리고 pH 9.0 이상에서는 $B_{AC}2$형 반응이 일어난다. Volaton의 가수분해 반응성은 입체 장애보다는 양하전 크기$(p{\gg}{\alpha}C_2)$에 의존적이며 $pH\;7.0{\sim}9.0$ 사이에서는 이들 두 반응이 경쟁적으로 일어나는 반응 메카니즘을 제안하였다.